We know that the industrial fishing industry can often skirt the law in search of profits. In my decade of campaigning to rescue our oceans, I have seen dozens of ships fishing illegally, seen fish hidden in the inner bowels of fishing boats and witnessed industry officials lie to the faces of politicians.

This is just one of the many reasons that we at Greenpeace are working to change the way we catch and buy fish all over the world. And today details emerged about one of the world's largest fishing companies, South Korea-based Dongwon Industries, which will hopefully encourage action by governments, consumers and retailers across the world.

Dongwon owns fishing boats and tuna brands – including US tuna brand StarKist – all over the world. Dongwong and Starkist are also members of the International Seafood Sustainability Foundation, a group with the intended purpose to ensure legality and sustainability of its members’ tuna products.

But these intentions again amount to little as it has been revealed that a Dongwon fishing boat, the F/V Premier, (which is under investigation for fishing illegally in Liberian waters in 2011 and 2012), had also fabricated a letter from the Liberian government implying that the allegations of illegal fishing were a misunderstanding and that it was allowed to fish in Liberian waters.

This is a series of very serious criminal offences and shows the depth this company is willing to go to in order to manipulate governments and to continue its pillage of our dwindling tuna resources for its own profits.

Greenpeace has been working in Africa and across the Pacific and Indian oceans to keep destructive and illegal fishing activities out – and to empower local communities to have more ownership and benefits of their ocean resources. We have consistently been putting pressure on governments and international oceans management bodies to end illegal fishing and have demanded action from markets to ensure they do not buy from companies engaged in illegal and unsustainable fishing.

In Korea, we have been urging Dongwon to clean up its act for several years. Last year, Dongwon topped Greenpeace East Asia’s ranking as the most unsustainable tuna brand in Korea. The company has not responded with any solid policies or intentions to clean up its act and to ensure sustainable and legal tuna products, including in the US where its brand Starkist is a market leader.

Today we are asking the South Korean government to call Dongwon's ship back home, conduct an independent investigation into how these latest activities could take place under its watch and impose an effective sanction, such as revoking the F/V Premier’s licence.

If we want healthy oceans, ample seafood and sustainable fishing jobs for the future, we need fishing operations to act responsibly at sea today. While this instance of the F/V Premier may just be one boat, we know that too often, what happens at sea stays at sea and we’re none the wiser.

We’re working to pressure the South Korean government to do the right thing – and calling on retailers to ensure they do not purchase tuna that could come from illegal sources such as this. Watch this space for future updates.

Sari Tolvanen is an oceans campaigner based in Greenpeace International’s Amsterdam office